Results
Cost-effectiveness
The total costs per patient for intervention and usual care were €2,221 and €2,448, respectively within the 1-year time horizon in the basecase (Figure 2). This reflects a cost saving of €227 (95%CI: €58-€403) per patient for the PHARMACOP-intervention. Also, the PHARMACOP-intervention resulted in a significant decrease of 0.07 (95%CI: 0.04–0.10) hospital-treated exacerbations per patient (0.177 for PHARMACOP versus 0.244 for usual care) when the intervention effect was applied for the first 3-months (Figure 3). In addition, a small (<0.001 QALYs) increase in QALYs gain was observed. Notably, the initial higher costs in the PHARMACOP-intervention (due to intervention costs and increased adherence) compared to usual care of €161 per patient were offset by €388 savings on expenses for treatment of exacerbations.
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Figure 2.
Summary of 1-year effects on costs.Usual care: Medication costs (850), Pharmacy fee (0), Exacerbation costs (1598), Total costs (2448); Intervention: Medication costs (934), Pharmacy fee (77), Exacerbation costs (1210), Total costs (2221); Difference (95% CI): Medication costs (84; 44–129), Pharmacy fee (77; 55–104), Exacerbation costs (-388; -225 - -560), Total costs (-227; -58 - -403).
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Figure 3.
Summary of 1-year effects on hospital-treated exacerbations.Usual care: Hospital Treated (HT) Exacerbations (0.24). Intervention: Hospital Treated (HT) Exacerbations (0.18). Difference (95% CI): Hospital Treated (HT) Exacerbations (-0.07; -0.04 - -0.10).
Sensitivity Analyses
Probabilistic sensitivity analyses revealed that >99% of the 3,000 simulations performed resulted in cost-savings for the PHARMACOP-intervention, often combined with positive incremental effects on both QALYs and hospital-treated exacerbations. This is illustrated in Figures 4 and 5: The majority of the simulations were situated in the South-Eastern quadrant of the cost-effectiveness plane. At a willingness to pay of €0 per QALY, the probability of the PHARMACOP-intervention being cost-effective was 99.4%.
In univariate sensitivity analyses, all relevant parameters were varied within their 95%CI of the basecase values. Figure 6 shows the model was most sensitive to the number of hospital-treated exacerbations in the PHARMACOP-trial and the relative risk reduction due to the intervention. The medication costs and adherence improvement were of somewhat less influence. However, the dominant situation of the PHARMACOP-intervention was retained in all univariate analyses.
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Figure 4.
Probabilistic sensitivity analyses for QALYs. QALY: Quality Adjusted Life-Year.
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Figure 5.
Probabilistic sensitivity analyses for hospital-treated exacerbations.
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Figure 6.
Univariate sensitivity analyses. CT: Community Treated; EDT: Emergency Department Treated; HT: Hospital Treated; RR: Relative Risk.
In scenario analyses ( Table 2 ) several variations of the intervention runtime, the time the adherence improvement would last, extensions of the time horizon and mean FEV1%pred were tested for their influence on cost-effectiveness. As no marked QALY differences were observed, this scenario analyses included costs and hospital-treated exacerbations only.
The PHARMACOP-intervention remained cost-saving with longer projected time horizons and different assumptions on the lasting effect on adherence. If the program runtime was as long as the time horizon, up to 1.36 hospital-treated exacerbations per patient were prevented in the 12.5 year time horizon. Cost savings were retained in most sensitivity analyses, except for the scenario where costs due to adherence improvement lasted for 12.5 years. Although the mean FEV1% pred did affect absolute number of hospital-treated exacerbations, the number of prevented hospital-treated exacerbations remained the same.